Heart disease is one of the leading causes of death and hospitalization among the elderly. The number of patients that reach an advanced phase of heart disease (e.g., end stage heart failure, refractory heart failure, or terminal heart failure) continues to increase due to improvements in the treatment of heart disease. Patients with end stage heart failure fall into stage D of the ABCD classification of the American College of Cardiology (ACC)/American Heart Association (AHA), and class of the New York Heart Association (NYHA) functional classification. These patients are characterized by advanced structural heart disease and pronounced symptoms of heart failure at rest or upon minimal physical exertion, despite maximal medical treatment according to current guidelines. This patient population has a one-year mortality rate of approximately fifty percent and requires special therapeutic interventions.
Treatment of end stage heart failure may include implant of a mechanical circulatory support device (e.g., a ventricular assist device, such as a left ventricular assist device) to aid the heart in pumping blood to the body. A ventricular assist device may be used to sustain life until a heart transplant procedure may be performed (i.e., as a bridge to transplant), as a permanent solution to reduce the symptoms of heart disease (i.e., destination therapy), or as a temporary measure to treat a reversible condition (such as, e.g., myocarditis). Though ventricular assist devices may be effective in the treatment or management of symptoms of heart failure, ventricular assist devices may be susceptible to adverse incidents, including, but not limited to, pump thrombosis.
Ventricular assist device pump thrombosis may be characterized as a partial or complete blockage of the flow of blood in or near the ventricular assist device. For example, a blockage may occur in the inflow cannula, such as near an inflow valve; in the pump body, such as a rotor, impeller, or stators; or in the outflow graft, such as near an outflow valve. The causes of pump thrombosis may be classified as either pump-related, patient-related, or management-related. Pump-related causes of pump thrombosis may include, e.g., heat generated by moving parts or outflow graft kinks. Patient-related causes of pump thrombosis are factors that render patient more likely to have thrombotic complications, e.g., atrial fibrillation, infection, or preexisting conditions. Management-related causes of pump thrombosis are due to surgical or medical protocol choices, e.g., implantation techniques, extent of anticoagulation, or low pump flow due to a low speed setting.
Pump thrombosis may be classified as suspected pump thrombus or confirmed pump thrombus. In suspected pump thrombus, the clinical patient condition, such as hemolytic urine, or pump parameters, such as power draw, may suggest thrombus on any of the blood-contacting surfaces of the ventricular assist device. Confirmation of pump thrombus is typically done by visual inspection (e.g., during device exchange, transplantation, autopsy), evaluation of radiographic evidence, or by detecting absence or reduction of Doppler inflow or outflow signals, or another measure of blood flow.